Method and device for loops-over-loops MRI coils

ABSTRACT

A method and apparatus for receiving (RX) radio-frequency (RF) signals suitable for MRI and/or MRS from MRI “coil loops” (antennae) that are overlapped and/or concentric, and each of which has a preamplifier and frequency-tuning circuitry and an impedance-matching circuitry, but wherein the loops optionally sized differently and/or located at different elevations (distances from the patient&#39;s tissue) in order to extract signal from otherwise cross-coupled coil loops and to improve signal-to-noise ratio (SNR) in images made from the received signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/619,051 filed Feb. 10, 2015, titled “Device and method forloops-over-loops MRI coils” (which issued as U.S. Pat. No. 10,191,128 onJan. 29, 2019), which claims benefit of U.S. Provisional PatentApplication 61/939,255 filed Feb. 12, 2014, titled “Device and methodfor loops-over-loops MRI coils,” each of which is incorporated herein byreference in its entirety.

FIELD OF THE INVENTION

This invention relates to the field of magnetic-resonance imaging (MRI)and magnetic-resonance spectroscopy (MRS), and more specifically to amethod and apparatus for transmitting (TX) and receiving (RX)radio-frequency (RF) signals suitable for MRI and/or MRS from MRI“coils” (antennae) that are overlapped and/or concentric, but optionallysized differently and/or located at different elevations (distances fromthe patient's tissue) in order to extract signal from otherwisecross-coupled coil loops and to improve signal-to-noise ratio (SNR) ofthe received signal.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 6,605,775 to Seeber et al. issued Aug. 12, 2003 with thetitle “Floating radio frequency trap for shield currents” and isincorporated herein by reference. In U.S. Pat. No. 6,605,775, Seeber etal. describe a floating shield current trap that provides first andsecond concentric tubular conductors electrically connected to provide aresonance-induced high impedance of current flow in a path consisting ofthe inner and outer conductors and their junctions thereby suppressingcoupled current flow on a shield of a conductor contained within thefirst inner tubular conductor.

U.S. Pat. No. 6,664,465 to Seeber issued Dec. 16, 2003 with the title“Tuning system for floating radio frequency trap” and is incorporatedherein by reference. In U.S. Pat. No. 6,664,465, Seeber describes afloating shield current trap provides two resonance loops formed ofsplit concentric tubular conductors joined radially at their axial ends.Adjustment of the separation of these loops provides a change incoupling between the loops effecting a simplified tuning of theresonance of the trap for different expected frequencies of interferingshield current.

U.S. Pat. No. 6,593,744 to Burl et al. issued Jul. 15, 2003 with thetitle “Multi-channel RF cable trap for magnetic resonance apparatus” andis incorporated herein by reference. In U.S. Pat. No. 6,593,744, Burl etal. describe a multi-channel RF cable trap that blocks stray RF currentfrom flowing on shield conductors of coaxial RF cables of a magneticresonance apparatus. An inductor is formed by a curved semi-rigid troughconstructed of an insulating material coated with an electricallyconducting layer. Preferably, the inductor and the cable follow an“S”-shaped path to facilitate good electromagnetic coupling. The RFcables are laid in the trough and the shield conductors inductivelycouple with the inductor. A capacitor and optional trim capacitor areconnected across the trough of the inductor to form a resonant LCcircuit tuned to the resonance frequency. The LC circuit inductivelycouples with the shield conductors to present a signal-attenuating highimpedance at the resonance frequency. The resonant circuit is preferablycontained in an RF-shielding box with removable lid.

Low-power circuits can use varactors (electrically variable capacitors),field-effect transistors (used as variable gain elements or variableresistors) and like components that are directlyelectrically-adjustable, for use in adjusting frequency, impedance orother circuit characteristics and parameters, however such componentsare often unsuitable or inoperative in high fields.

U.S. Pat. No. 6,495,069 issued Dec. 17, 2002 to Lussey et al. with thetitle “Polymer composition” and is incorporated herein by reference. InU.S. Pat. No. 6,495,069, Lussey et al. describe a polymer compositioncomprises at least one substantially non-conductive polymer and at leastone electrically conductive filler and in the form of granules. Theirelastomer material was proposed for devices for controlling or switchingelectric current, to avoid or limit disadvantages such as the generationof transients and sparks which are associated with the actuation ofconventional mechanical switches. They described an electrical conductorcomposite providing conduction when subjected to mechanical stress orelectrostatic charge but electrically insulating when quiescentcomprising a granular composition each granule of which comprises atleast one substantially non-conductive polymer and at least oneelectrically conductive filler and is electrically insulating whenquiescent but conductive when subjected to mechanical stress. They didnot propose a means for electrically activating such switches.

U.S. Pat. No. 8,299,681 to Snyder, Vaughan and Lemaire issued Oct. 30,2012 with the title “Remotely adjustable reactive and resistiveelectrical elements and method” and is incorporated herein by reference.In U.S. Pat. No. 8,299,681, Snyder, Vaughan and Lemaire describe anapparatus and method that includes providing a variable-parameterelectrical component in a high-field environment and based on anelectrical signal, automatically moving a movable portion of theelectrical component in relation to another portion of the electricalcomponent to vary at least one of its parameters. In some embodiments,the moving uses a mechanical movement device (e.g., a linear positioner,rotary motor, or pump). In some embodiments of the method, theelectrical component has a variable inductance, capacitance, and/orresistance. Some embodiments include using a computer that controls themoving of the movable portion of the electrical component in order tovary an electrical parameter of the electrical component. Someembodiments include using a feedback signal to provide feedback controlin order to adjust and/or maintain the electrical parameter. Someembodiments include a non-magnetic positioner connected to an electricalcomponent configured to have its RLC parameters varied by thepositioner.

U.S. Patent Application Publication Number 20100253348 by Wigginspublished Oct. 7, 2010 with the title “Radio Frequency Coil Arrangementfor High Field Magnetic Resonance Imaging with Optimized Transmit andReceive Efficiency for a Specified Region of Interest, and RelatedSystem and Method,” and is incorporated herein by reference. In theapplication, Wiggins describes exemplary embodiments of a coilarrangement that can include, e.g., a plurality of elements which can beprovided at an angle from one another. The angle can be selected toeffectuate an imaging of a target region of interest at least one of apredetermined depth or range of depths, for example. In certainexemplary embodiments according to the present disclosure, the angle canbe selected to effectuate an exemplary predetermined transmit efficiencyfor at least one of the elements. Additionally, the exemplary angle canbe selected to effectuate a predetermined receive sensitivity for atleast one of the elements. Further, according to certain exemplaryembodiments of a coil arrangement in according to the presentdisclosure, the angle can be adjusted manually and/or automatically.

A journal article, “96-Channel Receive-Only Head Coil for 3 Tesla:Design Optimization and Evaluation” by Graham C. Wiggins et al., Magn.Reson. Med. 2009 September; 62(3): 754-762. doi:10.1002/mrm.22028,describes a receive coil, and is incorporated herein by reference.

U.S. Pat. No. 4,885,539 to Roemer et al. issued Dec. 5, 1989 with thetitle “Volume NMR coil for optimum signal-to-noise ratio” and isincorporated herein by reference. In U.S. Pat. No. 4,885,539, Roemer etal. describe an RF volume coil with optimized signal-to-noise ratio, forNMR use, has a reduced length L_(c), which is between about 0.3r_(s) andabout 1.5r_(s), where r_(s) is the radius of asample-to-be-investigated, contained within the cylindrical volume coil,with the volume coil radius r_(c) being between about 1.0r_(s) and about1.6r_(s) the “short” volume coil has an improved SNR for a voxel locatedsubstantially on the central plane of the coil, relative to the SNR of a“normal”-length volume coil with L_(c) greater or equal to 4r_(s).

A journal article, “The NMR Phased Array” by P. B. Roemer et al., MagnReson Med. 1990 November; Vol. 16 Issue 262 pages 192-225; describes aphased array receive coil, and is incorporated herein by reference.Roemer et al. describe ways to overlap coil loops (circular loopsoverlapped by spacing the centers of the circular loops at 0.75diameter, and square loops by about 0.9 diameter; and the loops are allthe same size) to reduce mutual-induction interference.

U.S. Pat. No. 6,534,983 to Boskamp et al. issued Mar. 18, 2003 with thetitle “Multi-channel phased array coils having minimum mutual inductancefor magnetic resonance systems” and is incorporated herein by reference.In U.S. Pat. No. 6,534,983, Boskamp et al. describe a multi-channelphased array coil for use in a magnetic resonance (MR) system isdisclosed herein. The phased array coil includes N coils configured inan array, each of the N coils having a geometric shape and overlappingwith (N−1) coils to form an overlap area within the array. The geometricshape of each of the coils and the overlap area are configured to causea mutual inductance between every pair of the coils to be less than 10percent of the self-inductance of each of the N coils. At least fourcoils are provided in the phased array coil.

U.S. Pat. No. 6,538,441 issued to Watkins et al. on Mar. 25, 2003 withthe title “RF coil for reduced electric field exposure for use in veryhigh field magnetic resonance imaging” and is incorporated herein byreference. In U.S. Pat. No. 6,538,441, Watkins et al. describe an RFcoil assembly for a very high field Magnetic Resonance Imaging (MRI)system is provided. The RF coil assembly comprises a plurality ofconductors arranged cylindrically and disposed about a patient bore tubeof the MRI system. Each of the conductors is configured for the RF coilassembly to resonate at substantially high frequencies. Further, the RFcoil assembly comprises a plurality of capacitive elements disposedbetween and connecting respective ends of the conductors and furtherdisposed in a spaced-apart relationship with the patient bore tube. Thecapacitive elements are for electrically interconnecting the pluralityof conductors at the respective ends of the conductors.

U.S. Pat. No. 6,822,448 issued to Watkins et al. on Nov. 23, 2004 withthe title “RF coil for very high field magnetic resonance” and isincorporated herein by reference. In U.S. Pat. No. 6,822,448, Watkins etal. describe an RF coil assembly for a very high field MagneticResonance Imaging (MRI) system is provided comprising a plurality ofconductors arranged cylindrically and disposed about a cylindricalpatient bore tube of the MRI system and a plurality of capacitiveelements for electrically interconnecting the plurality of conductors atrespective ends of the conductors. The conductors have a width selectedfor the RF coil assembly to resonate at substantially high frequencies.A very high field Magnetic Resonance Imaging (MRI) system is providedthat comprises a RF coil assembly adapted to resonate at substantiallyhigh frequencies, a RF coil shield assembly and a plurality of RF drivepower cables.

There is a long-felt need for improved SNR from received signals in anMRI system.

SUMMARY OF THE INVENTION

The present invention provides overlapped and/or concentricradio-frequency (RF) MRI coils that are optionally located at differentelevations (distances from the patient's tissue) in order to extractsignal from cross-coupled coil loops and to improve signal-to-noiseratio (SNR) of the received signal. A large number of independentreceive pre-amplifiers (preamps) are used to collect the received signaland the MR image reconstructed from the received signal. In someembodiments, a plurality of preamps is connected to each of a pluralityof coil loops. In some embodiments, the received signals are decoded(e.g., using differential analog amplifiers on the analog signals, orare digitally processed to remove common mode signal, and to improveSNR.

In contrast to U.S. Pat. No. 6,534,983 to Boskamp et al., (where thegeometric shape of each of the coil loops and the overlap area areconfigured to cause a mutual inductance between every pair of the coilloops to be less than 10 percent of the self-inductance of each of the Ncoils) the present invention uses concentric and/or overlapped coilloops, each coil loop having one or more individual preamplifiers. Insome embodiments, the plurality of loops of the present invention willbe arranged to reduce mutual inductance, but the greater number of coilloops is used to advantage in order to achieve greater signal-to-noiseratio (SNR) in spite of the greater mutual inductance due to overlappingand/or concentric coil loops. The outputs of the plurality ofpreamplifiers are analyzed and decoded relative to one another toelectronically and/or computationally remove signal due to the mutualinductance between various pairs of the coil loops.

In some embodiments, a set of coil loops have each of their outputsphase shifted by possibly different amounts, and have their respectiveamplitudes varied by possibly different amounts, and their signals addedor subtracted from one another by decoder circuitry to improve the SNR.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a plan-view block diagram of a coil-loops system 101 having aplurality of overlapping and/or concentric coil loops 111, 112, 113, 114each connected to one of a plurality of RF receiver-electronics systems(e.g., capacitor 115, RF trap 116, preamplifier 117), according to someembodiments of the present invention.

FIG. 1B is a slightly-tilted elevational-view block diagram ofcoil-loops system 101, according to some embodiments of the presentinvention.

FIG. 1C is a slightly-tilted elevational-view block diagram ofcoil-loops system 103 having a plurality of overlapping and/orconcentric coil loops 111, 112, 113, 114 each connected to two of aplurality of sets of RF receiver-electronics systems (e.g., capacitor115, RF trap 116, preamplifier 117), according to some embodiments ofthe present invention.

FIG. 1D1 is a plan-view block diagram of a coil-loops system 104 havinga plurality of different-size-circumference concentric coil loops 111and loop 122 each connected to one of a plurality of RFreceiver-electronics systems (e.g., capacitor 115, RF trap 116,preamplifier 117), according to some embodiments of the presentinvention.

FIG. 1D2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 104, showing different-size-circumference loop 111 andloop 122 separated from one another by a vertical distance from thepatient being imaged, according to some embodiments of the presentinvention.

FIG. 1E1 is a plan-view block diagram of a coil-loops system 105 havinga plurality of different-size-circumference concentric coil loops 111,122 each connected to one of a plurality of RF receiver-electronicssystems (e.g., capacitor 115, RF trap 116, preamplifier 117), accordingto some embodiments of the present invention.

FIG. 1E2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 105, showing different-size-circumference loop 111 andloop 129 that are coplanar (not separated from one another by a verticaldistance from the patient being imaged), according to some embodimentsof the present invention.

FIG. 1F1 is a plan-view block diagram of a coil-loops system 106 havinga plurality of equal-size-circumference concentric coil loops 111 andloop 132 each connected to one of a plurality of RF receiver-electronicssystems (e.g., capacitor 115, RF trap 116, preamplifier 117), accordingto some embodiments of the present invention.

FIG. 1F2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 106, showing equal-size-circumference loop 111 andloop 132 separated from one another by a vertical distance from thepatient being imaged, according to some embodiments of the presentinvention.

FIG. 1G1 is a plan-view block diagram of a coil-loops system 107 havinga plurality of different-size-circumference concentric coil loop 111,and a plurality of smaller loops 129 each connected to one of aplurality of receiver-electronics systems (e.g., capacitor 115, RF trap116, preamplifier 117), according to some embodiments of the presentinvention.

FIG. 1G2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 107, showing different-size-circumference loop 111 andthe plurality of smaller loops 129 that are coplanar (not separated fromone another by a vertical distance from the patient being imaged),according to some embodiments of the present invention.

FIG. 1H1 is a plan-view photograph of coil-loops system 105 (see FIG.1E1 described above) having a plurality of different-size-circumferenceconcentric coil loop 111 and loops 129 each connected to one of aplurality of receiver-electronics systems (e.g., capacitor 115, RF trap116, preamplifier 117), according to some embodiments of the presentinvention.

FIG. 1H2 is an enlarged plan-view photograph of coil-loops system 105having a plurality of different-size-circumference concentric coil loop111 and loops 129 each connected to one of a plurality ofreceiver-electronics systems (e.g., capacitor 115, RF trap 116,preamplifier 117), according to some embodiments of the presentinvention.

FIG. 2 is a plan-view block diagram of a coil-loops system 201 having aplurality of overlapping and/or concentric coil loops 211, 212, 213, 214each connected to one or more of a plurality of RF receiver-electronicssystems (not shown), according to some embodiments of the presentinvention.

FIG. 3A is a plan-view block diagram of a coil-loops system 301 having aplurality of sets of concentric equal-size-circumference coil loops (theset that includes loops 311 and 313, and the set that includes loop 312and 314) each connected to one of a plurality of RF receiver-electronicssystems (not shown), according to some embodiments of the presentinvention.

FIG. 3B is a slightly-tilted elevational-view block diagram ofcoil-loops system 301, showing sets of concentricequal-size-circumference, the set that includes loops 311 and 313, andthe set that includes loop 312 and 314, separated from one another by avertical distance difference 399 measured from the patient being imaged,according to some embodiments of the present invention.

FIG. 4A is a plan-view block diagram of a coil-loops system 401 having aplurality of sets of non-concentric equal-size-circumference coil loops(the set that includes loops 411 and 413, and the set that includes loop412 and 414) each connected to one of a plurality of RFreceiver-electronics systems (not shown), according to some embodimentsof the present invention.

FIG. 4B is a slightly-tilted elevational-view block diagram ofcoil-loops system 401, showing sets of non-concentricequal-size-circumference, the set that includes loops 411 and 413, andthe set that includes loop 412 and 414, separated from one another by avertical distance difference 499 measured from the patient being imaged,according to some embodiments of the present invention.

FIG. 5A is a plan-view block diagram of a coil-loops system 501 having aplurality of sets of concentric different-size-circumference coil loops(the set that includes loops 511 and 513, and the set that includes loop512 and 514) each connected to one of a plurality of RFreceiver-electronics systems (not shown), according to some embodimentsof the present invention.

FIG. 5B is a slightly-tilted elevational-view block diagram ofcoil-loops system 502, showing sets of concentricdifferent-size-circumference, the set that includes loops 511 and 513,and the set that includes loop 512 and 514, separated from one anotherby a vertical distance difference 599 measured from the patient beingimaged, according to some embodiments of the present invention.

FIG. 5C is a slightly-tilted elevational-view block diagram ofcoil-loops system 503, showing sets of concentricdifferent-size-circumference, the set that includes loops 511 and 513,and the set that includes loop 512 and 514, that are co-planar (notseparated from one another by a vertical distance measured from thepatient being imaged), according to some embodiments of the presentinvention.

FIG. 6 is a perspective-view block diagram of a MRI system 601 having aplurality of sets of coil loops each connected to one or more of aplurality of RF receiver-electronics systems (not shown), according tosome embodiments of the present invention.

FIG. 7 is a plan-view block diagram of coil-loops system 701, showingsets of concentric different-size-circumference loops, that are eitherco-planar or separated from one another by a vertical distancedifference measured from the patient being imaged, according to someembodiments of the present invention.

FIG. 8 is a plan-view block diagram of coil-loops system 801, showingsets of equal-size-circumference loops, that are either co-planar orseparated from one another by a vertical distance difference measuredfrom the patient being imaged, according to some embodiments of thepresent invention.

FIG. 9A is a plan-view block diagram of coil-loops system 901, showingsets of non-concentric different-size-circumference loops, that areeither co-planar or separated from one another by a vertical distancedifference measured from the patient being imaged, according to someembodiments of the present invention.

FIG. 9B is a slightly-tilted elevational-view block diagram ofcoil-loops system 901, showing sets of non-concentricdifferent-size-circumference loops, that are either co-planar orseparated from one another by a vertical distance difference measuredfrom the patient being imaged, according to some embodiments of thepresent invention.

FIG. 9C is a perspective-view block diagram of coil-loops system 901,showing sets of non-concentric different-size-circumference loops, thatare either co-planar or separated from one another by a verticaldistance difference measured from the patient being imaged, according tosome embodiments of the present invention.

FIG. 10 is a plan-view block diagram of coil-loops system 1001, showingsets of non-concentric equal-size-circumference loops, that are eitherco-planar or separated from one another by a vertical distancedifference measured from the patient being imaged, according to someembodiments of the present invention.

FIG. 11A is a plan-view block diagram of a single coil loop 1102connected to two receiver-electronics systems, according to someembodiments of the present invention.

FIG. 11B is a plan-view block diagram of a single coil loop 1103connected to three receiver-electronics systems, according to someembodiments of the present invention.

FIG. 11C is a plan-view block diagram of a single coil loop 1104connected to four receiver-electronics systems, according to someembodiments of the present invention.

FIG. 12A is a plan-view block diagram of a coil-loops system 1201 havinga plurality of sets of concentric different-size-circumference coilloops (the set 1210 and the set 1280) each connected to one of aplurality of RF receiver-electronics systems (not shown), according tosome embodiments of the present invention.

FIG. 12B is a slightly-tilted elevational-view block diagram ofcoil-loops system 1201 having a plurality of sets of concentricdifferent-size-circumference coil loops (the set 1210 and the set 1280),separated from one another by a vertical distance difference 1299measured from the patient being imaged, according to some embodiments ofthe present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

Although the following detailed description contains many specifics forthe purpose of illustration, a person of ordinary skill in the art willappreciate that many variations and alterations to the following detailsare within the scope of the invention. Accordingly, the followingpreferred embodiments of the invention are set forth without any loss ofgenerality to, and without imposing limitations upon the claimedinvention. Further, in the following detailed description of thepreferred embodiments, reference is made to the accompanying drawingsthat form a part hereof, and in which are shown by way of illustrationspecific embodiments in which the invention may be practiced. It isunderstood that other embodiments may be utilized and structural changesmay be made without departing from the scope of the present invention.

The leading digit(s) of reference numbers appearing in the Figuresgenerally corresponds to the Figure number in which that component isfirst introduced, such that the same reference number is used throughoutto refer to an identical component which appears in multiple Figures.Signals and connections may be referred to by the same reference numberor label, and the actual meaning will be clear from its use in thecontext of the description.

As used herein, a non-magnetic mechanical movement device is anyelectrically-controlled device (such as a linear positioner, rotarymotor, or pump) made of materials that do not move (or move to asubstantially negligible amount) due to a high magnetic field whensubjected to the high magnetic field. Such devices can be placed withinthe high magnetic field of a magnetic-resonance machine or thesuperconducting magnet of a particle accelerator without the danger ofthe device moving due to the magnetic field and/or without theundesirable result of changing the magnetic field due to their presence.In many of the descriptions herein, the term “motor” (such as motor 140)will be used as an example of such a non-magnetic mechanical movementdevice, however one of skill in the art will recognize that in otherembodiments, the “motor” can be implemented as a linear or rotary motordevice using suitable linkages, or as a pump that uses a liquid orpneumatic fluid to effectuate the described movement.

FIG. 1A is a plan-view block diagram of a coil-loops system 101 having afirst set 110 of coils loops that includes a plurality of concentriccoil loops 111, 112, 113, 114 each connected to one of a plurality of RFreceiver-electronics systems (e.g., capacitor 115, RF trap 116,preamplifier 117), according to some embodiments of the presentinvention. In some embodiments, each of the first set of concentric coilloops 111, 112, 113, 114 has its own set of receiver-electronics units,each including at least one frequency-tuning capacitor (e.g., 194 forloop 111, and corresponding frequency-tuning capacitors on coil loops112, 113, 114), its own an impedance-matching capacitor (e.g., 115 forloop 111, and corresponding an impedance-matching capacitors on coilloops 112, 113, 114), its own RF trap (e.g., 116 for loop 111, andcorresponding RF traps on coil loops 112, 113, 114), and its own pre-amp(e.g., 117 for loop 111, and corresponding pre-amps on coil loops 112,113, 114). In some embodiments, each of the other overlapping andnon-concentric loops has its own receiver-electronics unit (for clarity,those are not shown). In some embodiments, a second set 180 ofconcentric coil loops 181, 182, 183, 184 are located offset to the sideof the first set 110 of concentric coil loops 111, 112, 113, 114, andeach of those has its own set of receiver-electronics units (forclarity, those are not shown). In some embodiments, the plurality ofreceiver-electronics units each generates an output signal (in someembodiments, each output signal is a differential pair of signals), andthese output signals are coupled to a signal decoder 118 that isconfigured to remove common-mode signals from the respective outputsignals based on others of the plurality of output signals, and theoutput of the signal decoder 118 is coupled to an imager 119 that, insome embodiments, uses conventional techniques to generate image slicesof the patient being imaged, and stores the images for later analysis(e.g., usually this is done by a radiologist trained to interpret theimages).

FIG. 1B is a slightly-tilted elevational-view block diagram ofcoil-loops system 101, according to some embodiments of the presentinvention. In some embodiments, a first geometric plane contains loops111 and 181, a second geometric plane contains loops 112 and 182, athird geometric plane contains loops 113 and 183, and a plurality ofother overlapping loops including loops 123, 133, 143, 153, 163 and 173,and others that are not individually labeled with reference numbers, afourth geometric plane contains loops 111 and 181, and a plurality ofother overlapping loops including loops 124, 134, 144, 154, 164 and 174,and others that are not individually labeled with reference numbers. Insome embodiments, the first geometric plane is separated from the secondgeometric plane by a distance 197, the second geometric plane isseparated from the third geometric plane by a distance 198, and thethird geometric plane is separated from the fourth geometric plane by adistance 199. Other aspects of the items in FIG. 1B are as set forthabove for FIG. 1A. Note that FIG. 1B is a slightly-tiltedelevational-view because the four geometric planes will show as singlelines when viewed edge-on, which does not convey the idea shown here.

FIG. 1C is a slightly-tilted elevational-view block diagram ofcoil-loops system 103 having a plurality of overlapping and/orconcentric coil loops 111, 112, 113, 114 each connected to two of aplurality of sets of RF receiver-electronics systems 195 (e.g.,capacitor 115, RF trap 116, preamplifier 117) and 196, according to someembodiments of the present invention. The main difference between system103 and system 101 described above is that each of a plurality of theantenna-receiver loops in system 103 has a plurality ofreceiver-electronics units, each with its own respective preamplifierreceiving signals from spaced-apart locations on the respective loops.In the example shown here, two receiver-electronics units are connectedto concentric coil loops 111, 112, 113, 114.

Note that as used herein, “concentric” loops are loops whose centers areon a single line perpendicular to the surface of the patient (e.g., avertical line of the surface of the patient is in a horizontal plane).“Concentric” loops may be in planes that are spaced apart as shown inFIG. 1B and FIG. 1C, or in co-planar configurations such as shown inFIG. 1E2 described below. In the latter case (such as shown in FIG.1E2), the loops are referred to as “concentric and co-planar.” In theformer case (such as shown in FIG. 1D2, FIG. 3A and FIG. 3B), the loopsare referred to as “concentric and spaced apart.” In the cases such asshown in FIG. 4A and FIG. 4B), the loops are referred to as “bothlaterally offset and spaced apart.” In some embodiments, two loops arein planes that are both angled to one another (not parallel orco-planar) and having centers that are both on a line perpendicular tothe surface of the tissue being imaged but wherein the centers of thetwo loops are spaced apart, termed “loops on planes angled to oneanother and having spaced-apart loop centers.” In some embodiments, twoloops are in planes that are both angled to one another (not parallel orco-planar) and having centers that are both on the same point (notspaced apart), termed “loops on planes angled to one another and havingloop centers on a single point.”

FIG. 1D1 is a plan-view block diagram of a concentric-and-spaced-apartcoil-loops system 104 having a plurality of different-size-circumferenceconcentric coil loops 111 and loop 122 each connected to one of aplurality of RF receiver-electronics systems (e.g., capacitor 115, RFtrap 116, preamplifier 117), according to some embodiments of thepresent invention. In some embodiments, a dielectric substrate 149 isprovided, with loop 111 affixed to the outer major face (the top surfacein the drawing of FIG. 1D2) and loop 122 affixed to the inner(opposite-side) major face (the bottom surface in the drawing of FIG.1D2). In some such embodiments, the smaller loop 122 obtains image froma smaller-diameter shallower volume of tissue, while the larger loop 111obtains image from a larger-diameter deeper volume of tissue. In otherembodiments, the smaller loop 122 is mounted to the outer surface andthe larger loop 111 is mounted to the surface of substrate 149 that iscloser to the subject patient being imaged. In some embodiments,impedance-matching capacitor 125, RF trap 126, and preamplifier 127 arecoupled to one side of loop 122, while frequency-tuning capacitor 124 iscoupled to an opposite side (180 degrees away) of loop 122.

In some embodiments, (not shown), the plane of loop 111 and the plane ofloop 122 are at an angle to one another, in order to reducecross-coupling somewhat. In some embodiments, three or more loops areeach in planes that are angled (not parallel) to each of the otherloops.

FIG. 1D2 is a slightly-tilted elevational-view block diagram ofconcentric-and-spaced-apart coil-loops system 104, showingdifferent-size-circumference loop 111 and loop 122 separated from oneanother by a vertical distance from the patient being imaged, accordingto some embodiments of the present invention. Note that FIG. 1D2 is aslightly-tilted elevational-view because the two geometric planes wouldshow as two spaced apart but single lines when viewed edge-on, whichdoes not as clearly convey the idea shown here.

FIG. 1E1 is a plan-view block diagram of a coil-loops system 105 havinga plurality of different-size-circumference co-planar and concentriccoil loops 111, 129 each connected to one of a plurality of RFreceiver-electronics systems (e.g., capacitor 115, RF trap 116,preamplifier 117), according to some embodiments of the presentinvention. System 105 is substantially similar to system 104 describedabove, except that the plurality of different-size-circumference loopsare co-planar or substantially co-planar (i.e., as used herein, planesthat are within 2 mm of one another and/or within about five (5) degreesof tilt or less are termed to be “substantially co-planar”). In someembodiments, the coil loops have a common center point, or have centerpoints that are separated by more than 2 mm, but the planes of the loopsare tilted relative to one another by more than five degrees. In otherembodiments, the tilt of the planes is at least ten (10) degrees. Inother embodiments, the tilt of the planes is at least fifteen (15)degrees. In other embodiments, the tilt of the planes is at least twenty(20) degrees. In other embodiments, the tilt of the planes is at leasttwenty-five (25) degrees. In other embodiments, the tilt of the planesis at least thirty (30) degrees. In other embodiments, the tilt of theplanes is at least thirty-five (35) degrees. In other embodiments, thetilt of the planes is at least forty (40) degrees. In other embodiments,the tilt of the planes is at least forty-five (45) degrees.

In some embodiments, a plurality of the coil loops of any of theembodiments described herein are overlapped such that the center pointsof two loops are separated by less than 75% of the diameter of thesmaller of the two loops (or of the diameter of one loop if thediameters are the same). In some embodiments, a plurality of the coilloops of any of the embodiments described herein are overlapped suchthat the center points of two loops are separated by no more than 50% ofthe diameter of the smaller of the two loops (or of the diameter of oneloop if the diameters are the same). In some embodiments, a plurality ofthe coil loops of any of the embodiments described herein are overlappedsuch that the center points of two loops are separated by no more than33% of the diameter of the smaller of the two loops (or of the diameterof one loop if the diameters are the same). In some embodiments, aplurality of the coil loops of any of the embodiments described hereinare overlapped such that the center points of two loops are separated byno more than 20% of the diameter of the smaller of the two loops (or ofthe diameter of one loop if the diameters are the same).

FIG. 1E2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 105, showing different-size-circumference loop 111 andloop 129 that are coplanar (not separated from one another by a verticaldistance from the patient being imaged), according to some embodimentsof the present invention. Note that FIG. 1E2 is a slightly-tiltedelevational-view because the geometric planes of both loops would showas a single line when viewed edge-on, which does not as clearly conveythe idea shown here.

FIG. 1F1 is a plan-view block diagram of a coil-loops system 106 havinga plurality of equal-size-circumference concentric coil loops 111 andloop 132 each connected to one of a plurality of RF receiver-electronicssystems (e.g., capacitor 115, RF trap 116, preamplifier 117), accordingto some embodiments of the present invention. In some embodiments asshown here, the receiver electronics for the two loops are connected tothe two loops on the same or nearly the same side (i.e., above-below oneanother). In other embodiments (not shown), the receiver electronics forthe two loops are connected to the two loops on opposite or nearlyopposite side (i.e., 180 degrees away from one another). In still otherembodiments (not shown), a plurality of receiver electronics units areconnected to each of the two loops, and are connected to the two loopson angularly separated or opposite sides (i.e., for example, tworeceiver electronics units connected to each loop, but 90 degrees awayfrom one another, or three receiver electronics units connected to eachloop, but 60 degrees away from one another).

FIG. 1F2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 106, showing equal-size-circumference loop 111 andloop 132 separated from one another by a vertical distance from thepatient being imaged, according to some embodiments of the presentinvention. Note the substrate layer of dielectric 149. In someembodiments, the two loops 111 and 132 are deposited on opposite majorfaces of substrate 149, to provide vertical separation (i.e., separationof the planes in a direction perpendicular to the surface of thepatient.

FIG. 1G1 is a plan-view block diagram of a coil-loops system 107 havinga plurality of different-size-circumference concentric coil loop 111,and a plurality of smaller loops 129 each connected to one of aplurality of receiver-electronics units (e.g., capacitor 115, RF trap116, preamplifier 117), according to some embodiments of the presentinvention. In some embodiments, the plurality of output signals from thevarious receiver-electronics units are decoded to remove common-modesignals and to distinguish signals from a plurality of laterally offsetvolumes (under the plurality of laterally offset loops 129) of tissuebeing imaged, which is done by signal decoder 118.

FIG. 1G2 is a slightly-tilted elevational-view block diagram ofcoil-loops system 107, showing different-size-circumference loop 111 andthe plurality of smaller loops 129 that are coplanar (not separated fromone another by a vertical distance from the patient being imaged),according to some embodiments of the present invention.

FIG. 1H1 is a plan-view photograph of one embodiment of coil-loopssystem 105 (see FIG. 1E1 described above) having a plurality ofdifferent-size-circumference concentric coil loop 111 and loops 129 eachconnected to one of a plurality of receiver-electronics systems (e.g.,capacitor 115, RF trap 116, preamplifier 117), according to someembodiments of the present invention.

FIG. 1H2 is an enlarged plan-view photograph of the embodiment ofcoil-loops system 105 having a plurality of different-size-circumferenceconcentric coil loop 111 and loops 129 each connected to one of aplurality of receiver-electronics systems (e.g., the outer loop 111having tuning capacitor 194, and a circuit board holding matchingcapacitor 115, RF trap 116, preamplifier 117, and the inner loop 129having tuning capacitor 124, and a circuit board holding matchingcapacitor 125, RF trap 126, preamplifier 127), according to someembodiments of the present invention.

FIG. 2 is a plan-view block diagram of a coil-loops system 201 having aplurality of concentric coil loops 211, 212, 213, 214 each connected toone or more of a plurality of RF receiver-electronics systems (notshown), and optionally overlapping or partially overlapping with anotherplurality of concentric coil loops 281, 282, 283, 284 according to someembodiments of the present invention. System 201 is similar to system101 of FIG. 1A, but while system 101 has a hexagonal array of coils(e.g., the six larger coil loops 123, 133, 143, 153, 163 and 173 thatsurround loop 113, and the six smaller coil loops 124, 134, 144, 154,164 and 174 that surround loop 114, have centers at points that formhexagonal shapes), the coil loops of system 201 are on rectangularCartesian coordinates (e.g., the eight smaller coil loops 215, 225, 235,217, 237, 216, 226, and 236 that surround loop 214 have centers thatform a rectangular grid).

FIG. 3A is a plan-view block diagram of a coil-loops system 301 having aplurality of sets of concentric equal-size-circumference coil loops (theset 310 having solid lines that includes loops 311 and 313, and the set380 having dashed lines on thinner solid lines that includes loop 312and 314) each connected to one of a plurality of RF receiver-electronicssystems (not shown), according to some embodiments of the presentinvention. See FIG. 3B for a side view.

FIG. 3B is a slightly-tilted elevational-view block diagram ofcoil-loops system 301, showing sets of concentricequal-size-circumference, the set 310 that includes loops 311 and 313,and the set 380 that includes loop 312 and 314, separated from oneanother by a vertical distance difference 399 measured from the patientbeing imaged, according to some embodiments of the present invention. Insome embodiments, the plane of set 380 is parallel to but separated fromthe plane of set 310 by a distance 399.

FIG. 4A is a plan-view block diagram of a coil-loops system 401 having aplurality of sets of non-concentric equal-size-circumference coil loops(the set 410 having solid lines that includes loops 411 and 413, and theset 480 having dashed lines on thinner solid lines that includes loop412 and 414) each connected to one of a plurality of RFreceiver-electronics systems (not shown), according to some embodimentsof the present invention.

FIG. 4B is a slightly-tilted elevational-view block diagram ofcoil-loops system 401, showing sets of non-concentricequal-size-circumference, the set 410 having solid lines that includesloops 411 and 413, and the set 480 having dashed lines on thinner solidlines that includes loop 412 and 414, separated from one another by avertical distance difference 499 measured from the patient being imaged,according to some embodiments of the present invention. In someembodiments, the plane of set 480 is parallel to but separated from theplane of set 410 by a distance 499.

FIG. 5A is a plan-view block diagram of a coil-loops system 501 having aplurality of sets of concentric different-size-circumference coil loops(the set that includes loops 511 and 513, and the set that includes loop512 and 514) each connected to one of a plurality of RFreceiver-electronics systems (not shown), according to some embodimentsof the present invention.

FIG. 5B is a slightly-tilted elevational-view block diagram ofcoil-loops system 502, (system 502 will have the plan view as system 501shown in FIG. 5A) showing sets of concentricdifferent-size-circumference, the set that includes loops 511 and 513,and the set that includes loop 512 and 514, separated from one anotherby a vertical distance difference 599 measured from the patient beingimaged, according to some embodiments of the present invention. In someembodiments, the plane of set 580 is parallel to but separated from theplane of set 510 by a distance 599.

FIG. 5C is a slightly-tilted elevational-view block diagram ofcoil-loops system 503, (system 503 will have the plan view as system 501shown in FIG. 5A) showing sets of concentricdifferent-size-circumference, the set that includes loops 511 and 513,and the set that includes loop 512 and 514, that are co-planar (notseparated from one another by a vertical distance measured from thepatient being imaged), according to some embodiments of the presentinvention. In some embodiments, the plane of set 580 is co-planar with(not separated from) the plane of set 510.

FIG. 6 is a perspective-view block diagram of a MRI system 601 having aplurality of sets of coil loops each connected to one or more of aplurality of RF receiver-electronics systems (not shown), according tosome embodiments of the present invention. In some embodiments, system601 includes a coil receiver system 610 (e.g., a plurality of coil loopsand receiver electronics units as described in any one or more of theother figures and descriptions herein) is placed in the bore of MRImagnet unit 640, and the signals from the plurality of coil loops andreceiver electronics units are decoded and imaged by units 118 and 119.

FIG. 7 is a plan-view block diagram of coil-loops system 701, showingsets of concentric different-size-circumference loops, that are eitherco-planar or separated from one another by a vertical distancedifference measured from the patient being imaged, according to someembodiments of the present invention.

FIG. 8 is a plan-view block diagram of coil-loops system 801, showingsets of equal-size-circumference loops, that are either co-planar orseparated from one another by a vertical distance difference measuredfrom the patient being imaged, according to some embodiments of thepresent invention.

FIG. 9A is a plan-view block diagram of coil-loops system 901, showingsets of non-concentric different-size-circumference loops, that areeither co-planar or separated from one another by a vertical distancedifference measured from the patient being imaged, according to someembodiments of the present invention.

FIG. 9B is a slightly-tilted elevational-view block diagram ofcoil-loops system 901, showing sets of non-concentricdifferent-size-circumference loops, that are either co-planar orseparated from one another by a vertical distance difference measuredfrom the patient being imaged, according to some embodiments of thepresent invention.

FIG. 9C is a perspective-view block diagram of coil-loops system 901,showing sets of non-concentric different-size-circumference loops, thatare either co-planar or separated from one another by a verticaldistance difference measured from the patient being imaged, according tosome embodiments of the present invention.

FIG. 10 is a plan-view block diagram of coil-loops system 1001, showingsets of non-concentric equal-size-circumference loops, that are eitherco-planar or separated from one another by a vertical distancedifference measured from the patient being imaged, according to someembodiments of the present invention. In some embodiments, two receiverelectronics units are connected to each one of the plurality of receivercoil loops, and the outputs of these are connected to decoder and imagerunits such as shown and described for other figures herein.

FIG. 11A is a plan-view block diagram of a single coil loop 1102connected to two spaced-apart receiver-electronics systems, according tosome embodiments of the present invention.

FIG. 11B is a plan-view block diagram of a single coil loop 1103connected to three spaced-apart receiver-electronics systems, accordingto some embodiments of the present invention.

FIG. 11C is a plan-view block diagram of a single coil loop 1104connected to four spaced-apart receiver-electronics systems, accordingto some embodiments of the present invention.

FIG. 12A is a plan-view block diagram of a coil-loops system 1201 havinga plurality of sets of concentric different-size-circumference coilloops (the set 1210 and the set 1280) each connected to one of aplurality of RF receiver-electronics systems (not shown), according tosome embodiments of the present invention.

FIG. 12B is a slightly-tilted elevational-view block diagram ofcoil-loops system 1201 having a plurality of sets of concentricdifferent-size-circumference coil loops (the set 1210 and the set 1280),separated from one another by a vertical distance difference 1299measured from the patient being imaged, according to some embodiments ofthe present invention.

The Figures herein show substantially circular coil loops that are usedin some embodiments. In other embodiments, square coil loops,rectangular coil loops, pentagonal and/or hexagonal coil loops, or othergeometric shapes are used. In some embodiments, combinations ofdifferent geometric shapes are used for the coil loops.

In some embodiments, the present invention provides an apparatus forreceiving radio-frequency (RF) signals suitable for magnetic-resonanceimaging (MRI) and/or magnetic-resonance spectroscopy (MRS) fromradio-frequency (RF) coils that are overlapped and/or concentric, butoptionally sized differently and/or located at different elevations(distances from the patient's tissue) in order to extract signal fromotherwise cross-coupled coil loops and to improve signal-to-noise ratio(SNR) of the received signal. This apparatus includes a substrate; aplurality of receiver-electronics units mounted on the substrate, eachgenerating an output signal; a plurality of RF receiver units affixed tothe substrate, each one of the plurality of RF receiver units includingan antenna loop connected to at least one of the plurality ofreceiver-electronics units; and decoder electronics operatively coupledto the plurality of RF receiver units and configured to removecommon-mode signals from the output signals from the plurality of RFreceiver units.

In some embodiments, each of the plurality of RF receiver units furtherincludes: a frequency-tuning capacitor, an impedance-matching capacitor,an RF trap, and a preamplifier.

In some embodiments, each of the plurality of RF receiver units furtherincludes: a least one frequency-tuning capacitor, a plurality ofimpedance-matching capacitors, a plurality of RF traps, and a pluralityof preamplifiers.

In some embodiments, the present invention provides an apparatus forreceiving radio-frequency (RF) signals suitable for magnetic-resonanceimaging (MRI) and/or magnetic-resonance spectroscopy (MRS) fromradio-frequency (RF) coils that are overlapped and/or concentric, butoptionally sized differently and/or located at different elevations(distances from the patient's tissue) in order to extract signal fromotherwise cross-coupled coil loops and to improve signal-to-noise ratio(SNR) of the received signal. The apparatus includes a substrate havinga first major surface and a second major surface; a first plurality ofreceiver-electronics units mounted on the substrate, wherein the firstplurality of receiver-electronics units includes a firstreceiver-electronics unit and a second receiver-electronics unit, andwherein each one of the first plurality of receiver-electronics unitsgenerates an output signal; a plurality of RF receiver units affixed tothe substrate, wherein the plurality of RF receiver units includes afirst RF receiver unit having a first antenna loop that is connected tothe first receiver-electronics unit and a second RF receiver unit havinga second antenna loop that is connected to the firstreceiver-electronics unit; and decoder electronics operatively coupledto receive the output signals from the plurality of RF receiver unitsand configured to remove common-mode signals from the output signalsfrom the plurality of RF receiver units.

In some embodiments, each of the plurality of RF receiver units furtherincludes a frequency-tuning capacitor, an impedance-matching capacitor,an RF trap, and a preamplifier.

In some embodiments, each of the plurality of RF receiver units furtherincludes a least one frequency-tuning capacitor, a plurality ofimpedance-matching capacitors, a plurality of RF traps, and a pluralityof preamplifiers.

In some embodiments, the first antenna loop is affixed to the firstmajor surface of the substrate and the second antenna loop is affixed tothe second major surface such that the first antenna loop overlaps thesecond antenna loop such that a line perpendicular to the first majorsurface and passing through a center point of the first antenna loop islaterally offset from a center point of the second antenna loop. In somesuch embodiments, the apparatus further includes a second plurality ofreceiver-electronics units mounted on the substrate, wherein the secondplurality of receiver-electronics units includes a thirdreceiver-electronics unit operatively coupled to receive signals fromthe first antenna loop and a fourth receiver-electronics unitoperatively coupled to receive signals from the second antenna loop, andwherein each one of the first plurality of receiver-electronics unitsgenerates its respective output signal and each one of the secondplurality of receiver-electronics units generates its respective outputsignal, and the respective output signals are combined and decoded bythe decoder electronics.

In some embodiments, the first antenna loop is affixed to the firstmajor surface of the substrate and the second antenna loop is affixed tothe second major surface and centered over the first antenna loop suchthat a center point of the first antenna loop and a center point of thesecond antenna loop are both located on a single line perpendicular tothe first major surface.

In some embodiments, the first antenna loop is affixed to the firstmajor surface of the substrate and the second antenna loop is affixed tothe second major surface and laterally offset from the first antennaloop such that a center point of the first antenna loop and a centerpoint of the second antenna loop are each located on one of twospaced-apart lines perpendicular to the first major surface.

In some embodiments, the first antenna loop is affixed to the firstmajor surface of the substrate and the second antenna loop is affixed tothe first major surface and centered relative to the first antenna loopsuch that a center point of the first antenna loop and a center point ofthe second antenna loop are located within two millimeters from oneanother, and wherein the first antenna loop and the first antenna loopare substantially coplanar.

In some embodiments, the first antenna loop is affixed to the firstmajor surface of the substrate and the second antenna loop is affixed tothe first major surface and laterally offset relative to the firstantenna loop, and wherein the first antenna loop and the first antennaloop are substantially coplanar and have sizes that differ by more thanten percent.

In some embodiments, the first antenna loop is affixed to the firstmajor surface of the substrate and the second antenna loop is orientedsuch that a plane of the second antenna loop is at an angle of at leastten degrees from a plane of the first antenna loop and centered relativeto the first antenna loop such that a center point of the first antennaloop and a center point of the second antenna loop are located withintwo millimeters from one another.

In some embodiments, the present invention provides a method forreceiving radio-frequency (RF) signals suitable for magnetic-resonanceimaging (MRI) and/or magnetic-resonance spectroscopy (MRS) fromradio-frequency (RF) coils that are overlapped and/or concentric, butoptionally sized differently and/or located at different elevations(distances from the patient's tissue) in order to extract signal fromotherwise cross-coupled coil loops and to improve signal-to-noise ratio(SNR) of the received signal. This method includes providing asubstrate, a plurality of receiver-electronics units mounted on thesubstrate, each generating an output signal, a plurality of RF receiverunits affixed to the substrate, each one of the plurality of RF receiverunits including an antenna loop having a resonance frequency andconnected to at least one of the plurality of receiver-electronicsunits, and decoder electronics operatively coupled to the plurality ofRF receiver units; receiving RF MRI signals with the antenna loops;pre-amplifying the received RF MRI signals to generate output signals;and removing common-mode signals from the output signals.

Some embodiments of the method further include automatically adjustingelectrical parameters of the receiver-electronics units to adjust theirresonance frequency.

Some embodiments of the method further include automatically adjustingelectrical parameters of the receiver-electronics units to adjust theresonance frequency by moving a non-magnetic mechanical-movement device.

In some embodiments of the method, the receiver-electronics units eachincludes a plurality of pi networks arranged at different radialdirections around a shielded RF cable.

In some embodiments, the present invention provides a method forreceiving radio-frequency (RF) signals suitable for magnetic-resonanceimaging (MRI) and/or magnetic-resonance spectroscopy (MRS) fromradio-frequency (RF) coils that are overlapped and/or concentric, butoptionally sized differently and/or located at different elevations(distances from the patient's tissue) in order to extract signal fromotherwise cross-coupled coil loops and to improve signal-to-noise ratio(SNR) of the received signal. This method includes providing asubstrate, a plurality of receiver-electronics units mounted on thesubstrate, each generating an output signal, and a plurality of RFreceiver units affixed to the substrate, each one of the plurality of RFreceiver units including an antenna loop having a resonance frequencyand connected to at least one of the plurality of receiver-electronicsunits, and decoder electronics operatively coupled to the plurality ofRF receiver units; receiving RF MRI signals with the antenna loops;pre-amplifying the received RF MRI signals to generate output signals;and removing common-mode signals from the output signals.

In some embodiments, the method further includes automatically adjustingelectrical parameters of the receiver-electronics units to adjust theirresonance frequency.

In some embodiments, the method further includes automatically adjustingelectrical parameters of the receiver-electronics units to adjust theresonance frequency by moving a non-magnetic mechanical-movement device.

In some embodiments, the method further includes affixing the firstantenna loop to the first major surface of the substrate; and affixingthe second antenna loop to the second major surface such that the firstantenna loop overlaps the second antenna loop such that a lineperpendicular to the first major surface and passing through a centerpoint of the first antenna loop is laterally offset from a center pointof the second antenna loop. In some such embodiments, the method alsofurther includes providing a second plurality of receiver-electronicsunits mounted on the substrate, wherein the second plurality ofreceiver-electronics units includes a third receiver-electronics unitand a fourth receiver-electronics unit; operatively coupling the thirdreceiver-electronics to receive signals from the first antenna loop;operatively coupling the fourth receiver-electronics unit to receivesignals from the second antenna loop; generating respective outputsignals from each one of the first plurality of receiver-electronicsunits and each one of the second plurality of receiver-electronicsunits; and combining and decoding the respective output signals togenerate an MRI image.

In some embodiments, the method further includes affixing the firstantenna loop to the first major surface of the substrate; and affixingthe second antenna loop to the second major surface of the substratecentered over the first antenna loop such that a center point of thefirst antenna loop and a center point of the second antenna loop areboth located on a single line perpendicular to the first major surface.

In some embodiments, the method further includes affixing first antennaloop to the first major surface of the substrate; and affixing thesecond antenna loop to the second major surface of the substratelaterally offset from the first antenna loop such that a center point ofthe first antenna loop and a center point of the second antenna loop areeach located on one of two spaced-apart lines perpendicular to the firstmajor surface.

In some embodiments, the method further includes affixing first antennaloop to the first major surface of the substrate; and affixing thesecond antenna loop to the first major surface centered relative to thefirst antenna loop such that a center point of the first antenna loopand a center point of the second antenna loop are located within twomillimeters from one another, and wherein the first antenna loop and thefirst antenna loop are substantially coplanar and differing incircumference by at least ten percent.

In some embodiments, the method further includes affixing the firstantenna loop to the first major surface of the substrate; and affixingthe second antenna loop to the first major surface laterally offsetrelative to the first antenna loop, and wherein the first antenna loopand the first antenna loop are substantially coplanar and havecircumference sizes that differ by at least ten percent.

In some embodiments, the method further includes affixing the firstantenna loop to the first major surface of the substrate; andpositioning the second antenna loop such that a plane of the secondantenna loop is oriented at an angle of at least ten degrees from aplane of the first antenna loop and centered relative to the firstantenna loop such that a center point of the first antenna loop and acenter point of the second antenna loop are located within twomillimeters from one another.

In some embodiments, the present invention provides a non-transitorycomputer-readable medium having instructions stored thereon for causinga suitably programmed information processor to execute a method thatincludes receiving RF MRI signals with a plurality of antenna loopsmounted to a substrate; pre-amplifying the received RF MRI signals usinga plurality of receiver-electronics units to generate output signals;and removing common-mode signals from the output signals. In someembodiments, the medium contains instructions such that the methodfurther includes using a feedback signal operatively coupled to theprogrammable information-processing device to provide feedback controlin order to maintain an electrical parameter of the plurality ofreceiver-electronics units. In some embodiments, the medium containsinstructions such that the method further includes controllingresistance, inductance and capacitance (RLC) values of the plurality ofreceiver-electronics units.

In some embodiments, the present invention provides a non-transitorycomputer-readable medium having instructions stored thereon for causinga suitably programmed information processor to execute a method thatincludes: autocontrolling an electrical parameter of each of a pluralityof receiver-electronics units that is mounted to a MRI receiver coilunit. In some embodiments, the medium contains instructions such thatthe method further includes using a feedback signal operatively coupledto the programmable information-processing device to provide feedbackcontrol in order to maintain the electrical parameter of the pluralityof receiver-electronics units. In some embodiments, the medium containsinstructions such that the method further includes controllingresistance, inductance and capacitance (RLC) values of the plurality ofreceiver-electronics units.

In some embodiments, the present invention provides a non-transitorycomputer-readable medium having instructions stored thereon for causinga suitably programmed information processor to execute a method thatcomprises: autocontrolling an electrical parameter of an LC circuit thatis mounted to a case of a snap-on balun attached to a shielded RF cablethat has a peripheral shield conductor and at least one inner conductorfor carrying RF signals, wherein the LC circuit has a resonancefrequency at a frequency of RF signals carried on the at least one innerconductor, wherein the case includes a piercing structure electricallyconnected to the LC circuit and configured to pierce and electricallyconnect the LC circuit to the shield conductor of the shielded RF cable.

In some embodiments of the computer-readable medium, the method furtherincludes using a feedback signal operatively coupled to the programmableinformation-processing device to provide feedback control in order tomaintain the electrical parameter of the LC circuit.

In some embodiments of the computer-readable medium, the method furtherincludes controlling resistance, inductance and capacitance (RLC) valuesof the LC circuit.

It is to be understood that the above description is intended to beillustrative, and not restrictive. Although numerous characteristics andadvantages of various embodiments as described herein have been setforth in the foregoing description, together with details of thestructure and function of various embodiments, many other embodimentsand changes to details will be apparent to those of skill in the artupon reviewing the above description. The scope of the invention shouldbe, therefore, determined with reference to the appended claims, alongwith the full scope of equivalents to which such claims are entitled. Inthe appended claims, the terms “including” and “in which” are used asthe plain-English equivalents of the respective terms “comprising” and“wherein,” respectively. Moreover, the terms “first,” “second,” and“third,” etc., are used merely as labels, and are not intended to imposenumerical requirements on their objects.

What is claimed is:
 1. An apparatus for receiving radio-frequency (RF)signals suitable for magnetic-resonance imaging (MRI) fromradio-frequency (RF) antenna loops that are overlapped and/orconcentric, in order to receive signal and improve signal-to-noise ratio(SNR) of the received signal, the apparatus comprising: a substratehaving a first major surface and a second major surface; a plurality ofpairs of RF antenna loops affixed to the substrate including: a firstpair of RF antenna loops, a second pair of RF antenna loops, and a thirdpair of RF antenna loops, wherein each pair of RF antenna loops in theplurality of pairs of RF antenna loops includes a first RF antenna loopand a second RF antenna loop located such that a center point of thefirst antenna loop and a center point of the second antenna loop areboth located on a single line perpendicular to a plane of the first RFantenna loop, wherein the first pair of RF antenna loops and the secondpair of RF antenna loops are partially overlapped with one another,wherein the first pair of RF antenna loops and the third pair of RFantenna loops are partially overlapped with one another, and wherein thesecond pair of RF antenna loops and the third pair of RF antenna loopsare partially overlapped with one another; a first plurality of pairs ofRF receiver units affixed to the substrate including: a first pair of RFreceiver units connected to receive signals from the first pair of RFantenna loops, a second pair of RF receiver units connected to receivesignals from the second pair of RF antenna loops, and a third pair of RFreceiver units connected to receive signals from the third pair of RFantenna loops, wherein each one of the first plurality of pairs of RFreceiver units includes: a first RF receiver unit operatively connectedto the first RF antenna loop of the corresponding pair of RF antennaloops, and a second RF receiver unit operatively connected to the secondRF antenna loop of the corresponding pair of RF antenna loops; and afirst plurality of electronics units mounted on the substrate, whereinthe first plurality of electronics units includes: a first electronicsunit connected to receive and add signals from the first pair of RFreceiver units, a second electronics unit connected to receive and addsignals from the second pair of RF receiver units, and a thirdelectronics unit connected to receive and add signals from the thirdpair of RF receiver units, and wherein each one of the first pluralityof electronics units adds the signals from the corresponding pair of RFreceiver units in order to generate a decoded output signal that hasimproved SNR to form a first plurality of output signals; andelectronics operatively coupled to receive the first plurality of outputsignals from the first plurality of electronics units and configured toprocess the first plurality of output signals to generate MRI imageslices of a patient being imaged.
 2. The apparatus of claim 1, whereineach RF receiver unit of the plurality of pairs of RF receiver unitsfurther includes: a frequency-tuning capacitor, an impedance-matchingcapacitor, an RF trap, and a preamplifier.
 3. The apparatus of claim 1,wherein each RF receiver unit of the plurality of pairs of RF receiverunits further includes: at least one frequency-tuning capacitor, aplurality of impedance-matching capacitors, a plurality of RF traps, anda plurality of preamplifiers.
 4. The apparatus of claim 1, wherein thefirst antenna loop is affixed to the first major surface of thesubstrate and the second antenna loop is affixed to the second majorsurface, wherein the first antenna loop and the second antenna loop aresubstantially equal in size.
 5. The apparatus of claim 1, furthercomprising: a second plurality of pairs of RF receiver units mounted onthe substrate, wherein the second plurality of pairs of RF receiver ofpairs of RF receiver of pairs of RF receiver units includes a third ofRF receiver unit operatively coupled to receive signals from the firstantenna loop and a fourth RF receiver unit operatively coupled toreceive signals from the second antenna loop, and wherein each of thefirst plurality of pairs of RF receiver units generates its respectiveoutput signal and each of the second plurality of pairs of RF receiverunits generates its respective output signal, and the respective outputsignals are combined and decoded by the decoder electronics.
 6. Theapparatus of claim 1, wherein, for each pair of RF antenna loops in theplurality of pairs of RF antenna loops, the first antenna loop isaffixed to the first major surface of the substrate and the secondantenna loop is affixed to the second major surface and centered overthe first antenna loop such that a center point of the first antennaloop and a center point of the second antenna loop are both located on asingle line perpendicular to the first major surface.
 7. The apparatusof claim 1, wherein, for each pair of RF antenna loops in the pluralityof pairs of RF antenna loops, the first antenna loop is affixed to thefirst major surface of the substrate and the second antenna loop isaffixed to the first major surface and centered relative to the firstantenna loop such that a center point of the first antenna loop and acenter point of the second antenna loop are located within twomillimeters from one another, and wherein the first antenna loop and thefirst antenna loop are substantially coplanar.
 8. The apparatus of claim1, wherein, for at least one pair of RF antenna loops in the pluralityof pairs of RF antenna loops, the first antenna loop is affixed to thefirst major surface of the substrate and the second antenna loop isoriented such that a plane of the second antenna loop is at an angle ofat least ten degrees from a plane of the first antenna loop and centeredrelative to the first antenna loop such that a center point of the firstantenna loop and a center point of the second antenna loop are locatedwithin two millimeters from one another.
 9. The apparatus of claim 1,wherein, for each pair of RF antenna loops of the plurality of pairs ofantenna loops, the first antenna loop and the second antenna loop haveequal sizes and shapes.
 10. The apparatus of claim 1, wherein, for eachpair of RF antenna loops of the plurality of pairs of antenna loops, thefirst antenna loop and the second antenna loop are concentric, andwherein the second antenna loop is smaller than the first antenna loop.11. The apparatus of claim 1, wherein, for each pair of RF antenna loopsof the plurality of pairs of antenna loops, a corresponding one thefirst plurality of receiver-electronics units further includes a thirdreceiver-electronics unit that is connected to the first antenna loop.12. The apparatus of claim 1, wherein, for each pair of RF antenna loopsof the plurality of pairs of antenna loops, the first antenna loop andthe second antenna loop have substantially circular shapes.
 13. A methodfor receiving radio-frequency (RF) signals suitable formagnetic-resonance imaging (MRI) from radio-frequency (RF) antenna loopsthat are overlapped and/or concentric, in order to receive signal andimprove signal-to-noise ratio (SNR) of the received signal, the methodcomprising: providing a substrate, mounting a plurality of pairs ofantenna loops mounted to the substrate including: a first pair of RFantenna loops, a second pair of RF antenna loops, and a third pair of RFantenna loops, wherein each pair of RF antenna loops in the plurality ofpairs of RF antenna loops includes a first RF antenna loop and a secondRF antenna loop located such that a center point of the first antennaloop and a center point of the second antenna loop are both located on asingle line perpendicular to a plane of the first RF antenna loop,wherein the first pair of RF antenna loops and the second pair of RFantenna loops are partially overlapped with one another, wherein thefirst pair of RF antenna loops and the third pair of RF antenna loopsare partially overlapped with one another, and wherein the second pairof RF antenna loops and the third pair of RF antenna loops are partiallyoverlapped with one another; affixing a plurality of pairs of RFamplifiers to the substrate including: a first pair of RF amplifiersconnected to receive signals from the first pair of RF antenna loops, asecond pair of RF amplifiers connected to receive signals from thesecond pair of RF antenna loops, and a third pair of RF amplifiersconnected to receive signals from the third pair of RF antenna loops,wherein each one of the plurality of pairs of RF amplifiers includes: afirst RF amplifier operatively connected to the first RF antenna loop ofthe corresponding pair of RF antenna loops, and a second RF amplifieroperatively connected to the second RF antenna loop of the correspondingpair of RF antenna loops; and mounting a first plurality of electronicsunits on the substrate, wherein the first plurality ofreceiver-electronics units includes: a first electronics unit connectedto receive and add signals from the first pair of RF amplifiers, asecond electronics unit connected to receive and add signals from thesecond pair of RF amplifiers, and a third electronics unit connected toreceive and add signals from the third pair of RF amplifiers, andadding, by each respective electronics unit, the signals from therespective corresponding pair of RF amplifiers and generatingcorresponding output signal to form a first plurality of output signals,wherein each one of the plurality of pairs of RF receiver unitscorresponds to one of the plurality of pairs of antenna loops; receivingRF MRI signals with the plurality of pairs of antenna loops;pre-amplifying the received RF MRI signals using the plurality of pairsof RF amplifiers to generate the first plurality of pairs of outputsignals; for each respective pair of the first plurality of pairs ofoutput signals, adding the pair of signals to one another in order togenerate a decoded signal that has improved SNR; and processing thedecoded signals to generate MRI image slices of a patient being imaged.14. The method of claim 13, wherein each respective RF receiver unit ofthe plurality of pairs of RF receiver units has a resonance frequency,the method further comprising: automatically adjusting electricalparameters of the respective RF receiver units to adjust their resonancefrequency.
 15. The method of claim 13, wherein each respective RFreceiver unit of the plurality of pairs of RF receiver units has aresonance frequency, the method further comprising: automaticallyadjusting electrical parameters of each RF receiver unit of theplurality of pairs of RF receiver units to adjust the resonancefrequency by moving a non-magnetic mechanical-movement device.
 16. Themethod of claim 13, further comprising: affixing the first antenna loopto the first major surface of the substrate; and affixing the secondantenna loop to the second major surface, wherein the first antenna loopand the second antenna loop are substantially equal in size.
 17. Themethod of claim 16, further comprising: providing a second plurality ofpairs of RF receiver units mounted on the substrate, wherein the secondplurality of pairs of RF receiver units includes a third pair of RFreceiver units and a fourth pairs of RF receiver units; operativelycoupling the third pair of RF receiver units to receive signals from thefirst antenna loop; operatively coupling the fourth pair of RF receiverunits to receive signals from the second antenna loop; generatingrespective output signals from each of the first plurality of pairs ofRF receiver units and each of the second plurality of pairs of RFreceiver units; and combining and decoding the respective output signalsto generate an MRI image.
 18. The method of claim 13, wherein for eachpair of RF antenna loops in the plurality of pairs of RF antenna loopsthe method further includes: affixing the first antenna loop to thefirst major surface of the substrate; and affixing the second antennaloop to the second major surface of the substrate centered over thefirst antenna loop such that a center point of the first antenna loopand a center point of the second antenna loop are both located on asingle line perpendicular to the first major surface.
 19. The method ofclaim 13, wherein for each pair of RF antenna loops in the plurality ofpairs of RF antenna loops the method further includes: affixing firstantenna loop to the first major surface of the substrate; and affixingthe second antenna loop to the first major surface centered relative tothe first antenna loop such that a center point of the first antennaloop and a center point of the second antenna loop are located withintwo millimeters from one another, and wherein the first antenna loop andthe first antenna loop are substantially coplanar and differing incircumference by at least ten percent.
 20. A non-transitorycomputer-readable medium having instructions stored thereon for causinga suitably programmed information processor to execute a method, whereinthe method is suitable for an apparatus that includes: a substratehaving a first major surface and a second major surface, a plurality ofpairs of RF antenna loops affixed to the substrate including: a firstpair of RF antenna loops, a second pair of RF antenna loops, and a thirdpair of RF antenna loops, wherein each pair of RF antenna loops in theplurality of pairs of RF antenna loops includes a first RF antenna loopand a second RF antenna loop located such that a center point of thefirst antenna loop and a center point of the second antenna loop areboth located on a single line perpendicular to a plane of the first RFantenna loop, wherein the first pair of RF antenna loops and the secondpair of RF antenna loops are partially overlapped with one another,wherein the first pair of RF antenna loops and the third pair of RFantenna loops are partially overlapped with one another, and wherein thesecond pair of RF antenna loops and the third pair of RF antenna loopsare partially overlapped with one another; a plurality of pairs of RFreceiver units affixed to the substrate including: a first pair of RFreceiver units connected to receive signals from the first pair of RFantenna loops, a second pair of RF receiver units connected to receivesignals from the second pair of RF antenna loops, and a third pair of RFreceiver units connected to receive signals from the third pair of RFantenna loops, wherein each one of the plurality of pairs of RF receiverunits includes: a first RF receiver unit operatively connected to thefirst RF antenna loop of the corresponding pair of RF antenna loops, anda second RF receiver unit operatively connected to the second RF antennaloop of the corresponding pair of RF antenna loops; and a firstplurality of receiver-electronics units mounted on the substrate,wherein the first plurality of receiver-electronics units includes: afirst receiver-electronics unit connected to receive and add signalsfrom the first pair of RF receiver units, a second receiver-electronicsunit connected to receive and add signals from the second pair of RFreceiver units, and a third receiver electronics unit connected toreceive and add signals from the third pair of RF receiver units, andwherein the method comprises: receiving RF MRI signals with theplurality of pairs of antenna loops mounted to the substrate;pre-amplifying the received RF MRI signals using the plurality of pairsof RF receiver units to generate a first plurality of pairs of outputsignals; adding the signals from the corresponding pair of RF receiverunits the first plurality of output signals to one another in order togenerate a decoded signal that has improved SNR; and decoding therespective output signals to generate an MRI image of a patient.